Lex demos

Lex demos for CMPT 379

# the following script assumes you have logged into a CSIL Linux machine or equivalent

# the first step is to make sure you are in your home directory
$ cd $HOME

# get the lexdemos source files
$ git clone https://github.com/anoopsarkar/compilers-class-hw.git
# or if you already have this directory, then pull the new files
$ cd compilers-class-hw/lexdemos
$ git pull

# build all the demo lex programs
$ make  
# this will print out all the compilation steps as it builds the demo programs
# look at the makefile.simple example makefile to see how to write your own makefile

# START DEMO:
# look at each demo lex program and test it with some example inputs
$ cat demo1.lex
# each lex file starts with %%
# then each line has a regular expression followed by an action which is a C statement

# there are example inputs for each demo program in the file testfile.sh
# use grep to list all the lines for each demo program as follows:
$ grep demo1$ testfile.sh

# the above command will print out a command that is a test example for each demo.

# run each of the test examples for the demo. 
# check your understanding of the regular expression to see if you understand it
# you should understand why the input works if it does, 
# and why the input doesn't work when it doesn't

# then repeat for demo2, demo3, ... beginning from "START DEMO" above.

# testfile.output contains the expected output for each test example
# the following not print any differences:
$ sh testfile.sh > myoutput
$ diff myoutput testfile.output

# There are a couple of extra demos not covered by testfile.sh

# comments.lex
$ cat comments.lex
$ echo "/* this is a comment */ this is not " | ./comments  # removes "some" C style comments from text

# arithexp-re:
$ cat arithexp-re.lex
$ echo "2+3*5" | ./arithexp-re  # says 'yes' if the input is a valid arithmetic expression, 'no' if not

# lc:
$ cat lc.lex
$ cat lc.lex | ./lc   # counts the number of lines and characters in a file

# vowelywords:
$ cat vowelywords.lex
$ ./vowelywords < /usr/share/dict/words  # prints out words with all English vowels in them

# username:
$ cat username.lex
$ echo "username" | ./username  # prints out your user name (in Linux or other Unix-like systems)